On line isotope separation techniques (ISOL) for production of ion beams of short-lived radionuclides
require fast separation of nuclear reaction products from irradiated target materials followed by a transfer into
an ion source. As a first step in this transport chain the release of nuclear reaction products from refractory
metals has been studied systematically and will be reviewed. High-energy protons (500 - 1000 MeV) produce
a large number of radionuclides in irradiated materials via the nuclear reactions spallation, fission and
fragmentation. Foils and powders of Re, W, Ta, Hf, Mo, Nb, Zr, Y, Ti and C were irradiated with protons
(600 - 1000 MeV) at the Dubna synchrocyclotron, the CERN synchrocyclotron and at the CERN PS-booster
to produce different nuclear reaction products.
The main topic of the paper is the determination of diffusion coefficients of the nuclear reaction products
in the target matrix, data evaluation and a systematic interpretation of the data. The influence of the ionic
radius of the diffusing species and the lattice type of the host material used as matrix or target on the
diffusion will be evaluated from these systematics. Special attention was directed to the release of group I, II
and III-elements. Arrhenius plots lead to activation energies of the diffusion process.